1. Field of the Invention
The present invention relates to a content usage device and a network system, and a license information acquisition method for using a content which is a digital work such as music and video using license information distributed from a server, and further relates to a technology for effective use of license information.
2. Description of the Related Art
In recent years, systems that distribute contents, via the Internet or digital broadcasting, that are digital works such as music, video and games have been developed, and a part of them is now in a phase for practical use. For distributing these contents, the methodology of content usage control, which restricts the number of reproduction (play/playback) times, moving and copying of the distributed content, has also been examined from a viewpoint of copyright protection, etc.
The conventional systems, as disclosed in the Japanese Laid-Open Patent Application Nos. 2000-48076 and 2000-293439, have been modeled so that (i) a server distributes information (hereinafter referred to as “license information”) that is necessary for content usage and restricts a content usage rule, and (ii) a plurality of content usage devices on a network system at home (home network) use the content using the license information distributed from the server so as to reproduce it.
Also, the license information distributed from the server is held by individual content usage device, and the content usage device uses the content using the license information held by the content usage device itself.
However, according to the conventional content usage device and network system, only the content usage device that requests the server to distribute the license information can receive the license information and use it. That is, the content usage device cannot use the content using the license information distributed from the server if it does not hold the license information in itself, even if the other content usage device holds that license information. That is a problem.
Accordingly, the object of the present invention is, in consideration of the above problem, to provide a content usage device and a network system, and a license information acquisition method for effectively using license information distributed from a server.